System.InvalidCastException error

I am trying to catch the System.InvalidCastException error. If I put a number into the calculator the program runs ok. If the calculate button is pressed with nothing in the text boxes I get the casting error Conversion from string "" to type 'Decimal' is not valid. I understand why I am getting the error. I don't know what to do about it. I want the program to dump null data and go back to waiting for input from the user. Thanks

Your code seems to present the message box saying 'please enter a value' and then continues through the rest of the function after that. It doesn't exit to await new input. Also, you've nested your if loops. txtInWage.Text = "" is only tested if txtInHours.Text = "". Meaning txtInHours needs to equal an empty string before txtInWage is checked. If txtInHours has a value entered but txtInWage doesn't you've got a problem.